CE Article #4 Diagnosing Acute Pancreatitis in Dogs Kirstin Mix, DVM Christopher Jones, DVM, DACVIM Gulf Coast Veterinary Specialists Houston, Texas ABSTRACT: Canine acute pancreatitis is challenging to diagnose and treat. Because this disease has the potential for severe morbidity and mortality, accurate and timely diagnosis is important.The ideal diagnostic test would be highly sensitive and specific, practical, affordable, and readily available. Because no one diagnostic test fits these criteria, the diagnosis of acute pancreatitis must be made based on evidence from a variety of diagnostic tests and clinical judgment.This article reviews some of the tests available to diagnose pancreatitis. ancreatitis is the most common disease of for degradation of ingested proteins, fats, and the canine exocrine pancreas, but accurate polysaccharides. These digestive enzymes are P diagnosis and reliable treatment of this produced by the pancreatic acinar cells, where disease remain challenging. Based on a necropsy they are stored until the pancreas is stimulated study1 evaluating the prevalence of inflamma- to secrete them into the duodenum. Most dogs tory lesions within the pancreas, 64.4% of dogs have two pancreatic ducts: the pancreatic duct have histologic evidence of pancreatic inflam- and the accessory pancreatic duct (Figure 1). mation, although the clinical significance of Most pancreatic cells are pancreatic acinar cells. these lesions is not clear. In humans, it is sus- Approximately 1% to 2% of pancreatic cells are pected that up to 90% of cases of pancreatitis endocrine cells. remain unrecognized and undiagnosed.2 This Because pancreatic digestive enzymes can may also be the case in veterinary patients. damage normal tissues within the body (includ- Timely and accurate diagnosis of pancreatitis is ing the pancreas), the pancreas has several essential because pancreatitis can be associated defense mechanisms to protect itself from with significant morbidity and mortality. This autodigestion or damage from these digestive article reviews the sensitivity, specificity, and enzymes.3 The first defense mechanism of the practicality of the different diagnostic modalities pancreas against autodigestion or damage from available to diagnose pancreatitis. pancreatic enzymes is production, storage, and secretion of pancreatic digestive enzymes in Send comments/questions via email PANCREAS their inactive forms, called zymogens. Within [email protected] PHYSIOLOGY the pancreatic acinar cells, the zymogens are or fax 800-556-3288. The major function of the segregated into zymogen granules, thus protect- Visit CompendiumVet.com for exocrine pancreas is produc- ing other cellular contents from contact with full-text articles, CE testing, and CE tion, storage, and secretion of the zymogens. In healthy animals, zymogens test answers. digestive enzymes important are activated after they are secreted into the COMPENDIUM 226 March 2006 Diagnosing Acute Pancreatitis in Dogs CE 227 Table 1. Prevalence of Clinical Signs in Dogs with Pancreatitis7 Clinical Sign Prevalence Dehydration 97% Anorexia 91% Vomiting 90% Weakness 79% Abdominal pain 58% Diarrhea 33% Icterus 32% s because of inappropriate activation of zymogens to their a r a active forms within the pancreas, thereby resulting in P 3 a i autodigestion of pancreatic tissue. Following activation c e l e of pancreatic enzymes, pancreatic inflammation and F y necrosis may occur, resulting in activation of inflamma- b n o tory mediators and free radicals. Depending on the i t a r severity of inflammation, pancreatic edema may occur, t s u l resulting in leakage of pancreatic digestive enzymes into l I Figure 1. Most dogs have both a pancreatic duct and an the peritoneal space or the intravascular space. The body accessory pancreatic duct. The exocrine pancreas comprises is initially able to protect itself from damage due to the most of the pancreatic tissue. Pancreatic islets of Langerhans’ presence of pancreatic enzymes in the intravascular and comprise less than 5% of the pancreatic tissue. peritoneal spaces. α-Macroglobulins and other protease inhibitors exist in systemic circulation and can bind to the pancreatic digestive enzymes, thereby inactivating duodenum with exposure to the duodenal enzyme them and expediting their removal from the body. There enteropeptidase. The zymogen trypsinogen is initially is a finite supply of α-macroglobulins and protease activated to its active form, trypsin, releasing the protein inhibitors in circulation. Once this supply is exhausted, trypsin activation peptide. Trypsin then activates the the circulating digestive enzymes result in widespread other pancreatic zymogens to their active forms. inflammation and activation of the coagulation, fibri- Another defense mechanism of the pancreas against nolytic, and complement cascades. Affected individuals Neither serum amylase nor serum lipase testing is a sensitive or specific diagnostic test for pancreatitis in dogs. autodigestion is trypsin inhibitor, which inhibits trypsin may develop disseminated intravascular coagulation, activity in the event that this enzyme is inappropriately shock, and multiorgan failure.4 activated within the pancreatic acinar cells. Trypsin The clinical course of pancreatitis is highly variable, inhibitor is produced and stored along with the pancre- ranging from subclinical to life-threatening disease. atic zymogens.4 Because of the potential for life-threatening complica- Both acute and chronic forms of pancreatitis occur in tions, timely and accurate diagnosis of pancreatitis is dogs, with the acute form being more clinically recog- essential. The ideal diagnostic test for pancreatitis would nized. Acute pancreatitis is thought to occur primarily be highly sensitive and specific, practical, noninvasive, March 2006 COMPENDIUM 228 CE Diagnosing Acute Pancreatitis in Dogs Figure 2. Ultrasonography of pancreatitis. (Courtesy of Gulf Coast Veterinary Diagnostic Imaging) Ultrasonogram of a patient with pancreatitis. Note that the body of the pancreas appears large and the surrounding mesentery is Ultrasonogram of a patient with severe pancreatitis that hyperechoic. developed a pancreatic abscess. and readily available. It is also important that diagnostic the history and clinical signs associated with pancreatitis test results be available quickly, especially in critically ill have poor specificity because they may be associated patients. This article reviews the clinical history and with numerous other diseases. physical examination findings, imaging techniques, hematologic and biochemical findings, serologic testing, RADIOGRAPHY,ULTRASONOGRAPHY, and biopsy techniques involved in diagnosing acute pan- AND COMPUTED TOMOGRAPHY creatitis in dogs. The most commonly used imaging techniques for assessing the pancreas in veterinary patients are abdomi- HISTORY AND PHYSICAL EXAMINATION nal radiography and ultrasonography. In human medi- The clinical presentation of acute pancreatitis is cine, computed tomography (CT) is routinely used to highly variable. Many affected dogs have a mild, self- assess patients suspected of having pancreatitis.8 The limited course of disease, and some of these patients value of this imaging modality has not been widely eval- remain subclinical. It is suspected that most dogs with uated in diagnosing pancreatitis in veterinary patients. pancreatitis remain undiagnosed.2 Middle-aged, female Abdominal radiography should be performed in every dogs are more likely to develop acute pancreatitis than patient suspected of having pancreatitis. Radiographic are other patient populations.4,5 There is a clinical changes and specificity associated with pancreatitis are impression that this disease is more common in minia- variable but may include loss of detail in the cranial ture schnauzers and anecdotal evidence that pancreatitis abdomen, displacement of the stomach to the left, and is more likely to occur after consumption of a fatty displacement of the duodenum to the right or ventrally. meal.4 Other historical factors, such as abdominal The colon may be displaced caudally in some pa- trauma or exposure to certain drugs (e.g., azathioprine, tients.2,7,9,10 In a retrospective study7 of fatal cases of L-asparaginase, corticosteroids), may also raise clinical canine pancreatitis, only 24% of dogs had radiographic suspicion of pancreatitis.4–6 abnormalities attributable to pancreatitis. Therefore, In a study7 of dogs with fatal, acute pancreatitis, the abdominal radiography has a low sensitivity in diagnos- most common clinical signs were dehydration, anorexia, ing pancreatitis.11 The primary benefit of abdominal vomiting, weakness, abdominal pain, diarrhea, and radiography in patients suspected of having pancreatitis icterus (Table 1). Fever, renal failure, respiratory com- is that it allows assessment of other organs in the promise, cardiovascular shock, and multiorgan failure abdominal cavity. As previously discussed, clinical signs have also been recognized in patients with severe forms of pancreatitis are nonspecific and could be related to of acute pancreatitis.2,4 It is important to recognize that many other diseases of the abdomen, such as gastroin- COMPENDIUM March 2006 Diagnosing Acute Pancreatitis in Dogs CE 229 Biochemical Abnormalities in Patients with Pancreatitis • Increased total protein level • Azotemia • Increased alanine aminotransferase level • Increased alkaline phosphatase level • Increased bilirubin level • Increased cholesterol level • Hypocalcemia